Standard solutionDissolve an accurately weighed quantity of USP Bretylium Tosylate RS in Mobile phase, and dilute quantitatively, and stepwise if necessary, to obtain a solution having a known concentration of about 20 µg per mL.

Test solutionTransfer about 200 mg of Bretylium Tosylate, accurately weighed, to a 100-mL volumetric flask, dissolve in and dilute with Mobile phase to volume, and mix.

Chromatographic system (see Chromatography 621)The liquid chromatograph is equipped with a 265-nm detector and a 4.6-mm × 25-cm column that contains packing L11. The flow rate is about 1.9 mL per minute. Chromatograph the Standard solution, record the chromatograms, and record the peak responses as directed for Procedure: the relative standard deviation for replicate injections is not more than 3.0%.

ProcedureSeparately inject equal volumes (about 30 µL) of the Test solution and the Standard solution into the chromatograph, record the chromatograms, and measure the peak responses. The relative retention times are about 0.25, 0.74, 1.0, 1.27, 1.40 for tosylate ion, o-bromobenzyldimethylamine, bretylium, m-bromobenzyldimethylamine, and p-bromobenzyldimethylamine, respectively. The sum of the responses for all the peaks, excluding those of the bretylium and tosylate peaks, from the Test solution is not more than two times the bretylium response from the Standard solution (2%); and no individual peak response is greater than that of the bretylium peak from the Standard solution (1%).

AssayDissolve about 300 mg of Bretylium Tosylate, accurately weighed, in 50 mL of dioxane in a conical flask. Add 2 drops of crystal violet TS, and titrate with 0.025 N perchloric acid in dioxane to a blue-green endpoint. Perform a blank determination (see Titrimetry 541), and make any necessary correction. Each mL of 0.025 N perchloric acid is equivalent to 10.36 mg of C18H24BrNO3S.